Separate eGRID and AVERT Location enums

[ryanhu021]

Description
We have a Location enum that is based on locations in the eGRID dataset. However, both the eGRID and AVERT schemas currently use this enum, and AVERT has a different set of locations. Refactor the schema so that we have separate EgridLocation and AvertLocation enums.

For eGRID, the locations should remain the same as the existing enum.

For AVERT, the locations should be US and all available regions in the data spreadsheet.

Acceptance Criteria
Separate enums, EgridLocation and AvertLocation, based on available locations in the respective dataset.

Steps:

• In src/schema/egrid.ts, rename Location to EgridLocation. Update all references to match
• In src/schema/avert.ts, create a new AvertLocation enum. Modify the AvertRecord schema to use this type
• Update unit tests

Additional Information

• AVERT Data Spreadsheet